erfl(3) Linux Man Page - System Grab Bag

Name

erf, erff, erfl - error function

Library

Math library ( libm ", " -lm )

Synopsis

#include <math.h> 
double erf(double  x );
float erff(float  x );
long double erfl(long double  x );

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

erf()

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

erff() erfl()

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

Description

These functions return the error function of x, defined as

erf(x) = 2/sqrt(pi) * integral from 0 to x of exp(-t*t) dt

Return Value

On success, these functions return the value of the error function of x, a value in the range [-1,\ 1].

If x is a NaN, a NaN is returned.

If x is +0 (-0), +0 (-0) is returned.

If x is positive infinity (negative infinity), +1 (-1) is returned.

If x is subnormal, a range error occurs, and the return value is 2*x/sqrt(pi).

Errors

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Range error: result underflow (x is subnormal) An underflow floating-point exception ( FE_UNDERFLOW ) is raised.

These functions do not set errno.

Attributes

For an explanation of the terms used in this section, see attributes(7). allbox; lbx lb lb T{ erf()erff()erfl()

Interface	Attribute	Value
T}	Thread safety	MT-Safe

Standards

C11, POSIX.1-2008.

History

C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD.